S. Afr. J. Zoo!. 1983, 18(3) 305

the rocky communities of both lakes, particularly the species level and with regard to species proliferation and among the algal scrapers, insect pickers and zooplank­ adaptive radiation. tivores. Furthermore, the Lake Victoria species take Furthermore, the restriction of populations to hooks baited with worms or meat suggesting that, like habitat islands strongly suggests that intralacustrine the Mbuna, they are facultative opportunists as well allopatric speciation is the main cause of the considerable as specialist feeders. species richness in the rift valley lakes, and was a con­ (iv) Populations of the different rocky islands of Lake Vic­ tributory factor to speciation in Lake Victoria. toria are isolated and it appears that little migration occurs between them as the fishes show a reluctance ACKNOWLEDGEMENTS to cross the inimical deep habitats that separate islands. The generous hospitality and willing assistance given by the Limited migration does occur, however, as Van Oijen Chief Fisheries Officer, Mr A.J. Mathotho and two suc­ et al. (1981) found that a rocky jetty which was situated cessive Senior Fisheries Research Officers (Mr D.H. Eccles more than 100 m from the nearest rocky shore was in­ and Mr B.J. Mkoko) of the Malawi Fisheries Department habited by Haplochromis nigricans within months of is truly appreciated. Indeed all members of the Malawi its construction. Fisheries Department were most friendly and helpful, ad­ Another example of parallel evolution is demonstrated ding considerably to the pleasure of our stay in Malawi. by Paralabidochromis victoriae Greenwood, 1956. This Involved directly with the work of the project were Lake Victoria species is so similar to Labidochromis technical assistants Messrs D. Mandere, L.M. Phiri, H. vel/icans of with regard to its dentition, its Selemani and B. Thindwa as well as the diver-boatmen C. jaw structure and general morphology that it could have Kalima, E. Chioko and A. Chunga. Assistance was also been placed in the same . However, as the two species rendered by launch-masters, Messrs E.M. Chilanga, E. are endemic to different lakes and have separate phylo­ Chinula, W. W. Msyale; boat mechanic P. Msosa and genies, Greenwood (1956) chose to erect the genus SCUBA divers A. Chavula and G. Phiri. To these friends Paralabidochromis for the Lake Victoria species. Only one and colleagues we extend a heartfelt thanks. specimen of P. victoriae has been found and it is not known Mr Robin Brown took almost all of the photographs and whether the species frequents rocky zones, but as it differs was a willing diving partner throughout his stay in Malawi. from the other rock dwellers in that it lacks the minute scala­ The exporters of ornamental fish Messrs N. Edwards, E. tion of chest, nape and cheek (Lewis 1982) it is conceivable Fleet and S. Grant were always ready to assist in various that it is not a member of the rocky community. ways and also provided us with a great deal of interesting

. Lake Malawi and Lake Tanganyika are both deep, nar­ information. We thank them for their co-operation. )

0 row, long rift valley lakes with clear water and fairly ex­ The project received considerable support from the J .L.B. 1

0 tensive rocky shores. These lakes do not share a single cichlid Smith Institute of Ichthyology, Grahamstown. We thank 2 Professors M.N. Bruton, M.M. Smith and Mr P.B.N. d species, but the unique cichlid fauna of each exhibits several e t striking examples of convergent evolution. Both lakes sup­ Jackson. The bulk of the typing and clerical organization a d port speciose, colourful communities of small rock-dwelling was done by Mrs Huibre Tomlinson, assisted by Mesdames (

r fishes whose members appear to fill very similar ecological H. Kampondeni, S. Jambo, J. Pote, B. Stewart, D. Thomp­ e h roles in each lake and many have strong morphological son and J. Wright. Elizabeth M. Tarr produced most of s i l parallels. Indeed the close similarities of the fishes of these the illustrations with contributions coming from Messrs O. b u two lakes have occasioned comment before (Regan 1921, Gon, L. Laurenson and P. White. Mr R. Stobbs prepared P

e 1922; Fryer & lIes 1972; Lowe-McConnell 1975; Stiassny the photographic prints of the illustrations for publication. h t 1980; Lewis 1981; Yamaoka 1982). This remarkable degree Mr B. Ranchod sorted and catalogued the reference collec­ y

b of parallelism is well illustrated by the Petrochromis species tion and Mrs D. Cave assisted with the preparation of the

d of Lake Tanganyika which are very similar morphologically reference list. We are most grateful to all. e t (particularly with regard to dentition), behaviourally and The manuscript, or part of the manuscript, was read at n a ecologically to the species of Lake Malawi r Petrotilapia various stages by G. Boltt, G.M. Branch, M.N. Bruton, g (Fryer & lIes 1972; Liem 1980; Yamaoka 1982). Similarly, D.H. Eccles, G. Fryer, P.B.N. Jackson, D.S.C. Lewis, e c the genus Tropheus closely resembles members of the N.A.H. Millard, P.N. Reinthal, S.S.D. Robertson, P. n e

c Pseudotropheus tropheops species-complex, as indicated by Skelton, M.M. Smith and E. Vrba. We thank all these peo­ i l Regan (1921) when he erected the genus Pseudotropheus. ple for their time and effort. r e In addition, the Labidochromis species of Lake Malawi have Dr D.S.C. Lewis is thanked for assisting with identifica­ d n much in common with Tanganicodus irsacae of Lake tion and taxonomic problems, for assistance on field trips, u

y Tanganyika. for many valuable discussions, for preparing the jaws and a A further parallel is that populations of rock-frequenting teeth for illustrations and for giving us access to his papers w e t of Lake Tanganyika are usually restricted to par­ which are in preparation. a We thank S. Siegrief, D. John and S. Lazarek for G ticular geographic localities, being isolated from one another t

e by unsuitable habitats. A particularly good example is pro­ assisting with the identification of Aufwuchs. n i vided by Tropheus moori which exists as a number of dif­ The research programme was funded jointly by the South b a ferent geographic races, or perhaps subspecies, each differ­ African and Malawi Governments. This support is gratefully S

y ing from the others with respect to coloration (Marlier 1959; acknowledged and a particular word of thanks is extended b Matthes 1962; Fryer & lIes 1972). In addition, a number to all the Government officials involved in the running of d e of sibling species occur sympatrically (Marlier 1959; Fryer the project. c u & lIes 1972). Thus, in many respects the rock-frequenting Publication costs of this paper were met by the Bureau d o

r fishes of the three Great Lakes of Africa exhibit a re­ for Scientific Publications (South Africa) and by the South p e markable degree of parallelism at the community level, at African Department of Foreign Affairs and Information. R 306 S.-Afr. Tydskr. Dierk. 1983, 18(3)

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